SRA

Plant-pollinator relationships are vital for plant productivity, therefore also food webs and human well-being, with most wild flowering plants and crops relying on animal pollination, primarily by bees. Climate change threatens plant-pollinator relationships, amongst other threats, through habitat change and altering vegetation composition, potentially leading to desynchronisation of, changes in quality or quantity of or even loss of interactions with food resources. While many plants may be under threat, most knowledge on how this actually translates to bee food resources comes from small-scale studies, synthetic meta-analyses, or simulations, with limited clear evidence on larger scales. Here, we present the results of a systematic Europe-wide monitoring project on pollen collected by honey bees (Apis mellifera), the geographic and temporal distribution of resources and potential risks under varying climate change scenarios. Although the honey bee is not considered to be in decline5, we chose it as a model organism in our study due to its European-wide distribution, importance as a pollinator in agroecological systems and generalised foraging to reflect impacts of climatic change on overall bee resource diversity. We analysed 2,500 pollen samples collected at 310 locations over Europe between May and August 2023 using DNA metabarcoding and estimated plant resource temperature and precipitation niche distributions. We demonstrate that increasing temperatures and decreasing precipitation will significantly reduce the diversity of foraging resources throughout Europe, by pushing a wide array of resources over their critical limits at levels expected in short time frames. This decline remains a major concern even when considering resilience factors such as alternative resources through temporal or spatial shifts. Our findings underscore the urgent need to address climate change impacts on plant-pollinator systems, as the anticipated declines in plant resource diversity will severely disrupt bee nutrition with broader implications on ecosystem health and human food security.